The invention discloses an organic/inorganic photocatalytic compound film, which is formed by compounding a perfluorinated sulfonic acid resin and nano-TiO2, wherein the perfluorinated sulfonic acid resin serves as a carrier and a modifier, and the film is formed by flow casting; and the mass percentage of TiO2 in the compound film is between 5 and 20 percent. The invention also discloses a method for preparing the compound film. The method comprises the steps of: mixing the TiO2 nano-powder with N,N-dimethyl formamide, performing ultrasonic treatment on the mixture, drippinging a N,N-dimethyl formamide solution of the perfluorinated sulfonic acid resin into a suspension after the mixure is evenly dispersed, performing ultrasonic treatment on the suspension, then flow-casting the suspension on a base plate for film formation, and performing thermal treatment to obtain the TiO2/PSR compound film. The compound film and the preparation method have the advantages of simple process, low cost, high photocatalytic activity and good repeated photocatalytic activity.